arm{,64}/xen: Remove "EXPERIMENTAL" in the description of the Xen options

The Xen ARM API is stable since Xen 4.4 and everything has been
upstreamed in Linux for ARM and ARM64. Therefore we can drop "EXPERIMENTAL"
from the Xen option in the both Kconfig.
Signed-off-by: Julien Grall <julien.grall@linaro.org>
Cc: Russell King <linux@arm.linux.org.uk>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will.deacon@arm.com>
Cc: linux-arm-kernel@lists.infradead.org
Cc: linux-kernel@vger.kernel.org

arch/arm/Kconfig

@@ -1758,7 +1758,7 @@ config XEN_DOM0
 	depends on XEN
 
 config XEN
-	bool "Xen guest support on ARM (EXPERIMENTAL)"
+	bool "Xen guest support on ARM"
 	depends on ARM && AEABI && OF
 	depends on CPU_V7 && !CPU_V6
 	depends on !GENERIC_ATOMIC64

arch/arm64/Kconfig

@@ -317,7 +317,7 @@ config XEN_DOM0
 	depends on XEN
 
 config XEN
-	bool "Xen guest support on ARM64 (EXPERIMENTAL)"
+	bool "Xen guest support on ARM64"
 	depends on ARM64 && OF
 	select SWIOTLB_XEN
 	help